Hydrogeochemistry of iron, manganese, sulfur and organic matter in the Fraser River Delta aquifer system

这项研究的目的是建立一个框架，以了解和预测三角洲含水层-含水层系统中还原地下水的地球化学演化。在不列颠哥伦比亚省的弗雷泽河三角洲含水层系统，业主和监管机构正在努力管理污染和未受干扰地点的铁和锰含量较高的地下水。人们认识到，在厌氧条件下的有机物降解是导致高铁、高锰和砷等微量元素的过程的关键驱动因素。然而，对于有机质厌氧降解的地球化学途径，如何在模型中表示这些途径，以及如何在原地或异地表征有机质以便使模型可以参数化，我们的理解存在差距。有机质的来源，无论是沉积有机质还是来自池塘或土壤的表层，在许多情况下都是未知的。厌氧有机物的降解过程与铁、锰和硫相的还原相耦合，不能孤立地进行研究。提出了一种野外-实验室-模型一体化的研究方案。研究现场位于公元前温哥华的弗雷泽河三角洲体系。该方法取决于四个组成部分：1)自然系统的实地表征；评估和制定表征战略；2)样品的矿物学和生物地球化学分析；3)受控条件下的实验室实验；以及4)实地评估假说、整合和解释数据的机械建模。这里开发的框架将有助于应用于修复和环境评估等工程问题，并改善对未受干扰和受污染场地的管理。这项研究将适用于其他环境，如艾伯塔省的油砂、页岩气开发和南亚的大三角洲。

The goal of this research is to develop a framework to understand and predict the geochemical evolution of reducing groundwater in deltaic aquifer-aquitard systems. In the Fraser River Delta aquifer system in British Columbia, owners and regulators are struggling to manage groundwater with high iron and manganese concentrations at both contaminated and undisturbed sites. It is recognized that organic matter degradation under anaerobic conditions is the key driver of the processes leading to high iron, manganese and trace elements such as arsenic. However, there is a gap in our understanding of the geochemical pathways of anaerobic degradation of organic matter, how to represent those pathways in models and how to characterize organic matter in - or ex situ so that models can be parameterized. The source of the organic matter, whether detrial sedimentary organic matter or surface derived from ponds or soils is not known in many cases. The processes of anaerobic organic matter degradation are coupled to the reduction of phases of iron, manganese and sulfur and cannot be examined in isolation. An integrated field - laboratory - modeling research program is proposed here. The research field site is in the Fraser River Delta system in Vancouver BC. The methodology hinges upon four components: 1) field characterization of natural systems; assessment and development of characterization strategies; 2) mineralogical and biogeochemical analysis of samples; 3) laboratory experiments under controlled conditions; and 4) mechanistic modeling to evaluate hypotheses at the field scale, to integrate and to interpret data. The framework developed here will be useful in application to engineering problems such as remediation and environmental assessment and improve management of undisturbed and contaminated sites. The research will be applicable to other settings such as the oil sands of Alberta, shale gas developments, and the great deltas of South Asia.